x not equal to 0

Expert replies

Previous Topic Next Topic

bhumika.k.shah: Legendary Member; Posts: 941; Joined: Sun Dec 27, 2009 12:28 amFollowed by: 1 member; Thanked: 20 times

by bhumika.k.shah » Sun Jan 17, 2010 12:48 am

If x is not equal to 0 ,then (x + 1/x)^2 - (x - 1/x)^2=?

A. 1/x
B. x
C. 1
D. 2
E. 4

OA E

Can i plug in #s?

Like this post

Source: Beat The GMAT — Problem Solving | Sun Jan 17, 2010 12:48 am

ace_gre: Senior | Next Rank: 100 Posts; Posts: 98; Joined: Mon Nov 23, 2009 2:30 pmFollowed by: 1 member; Thanked: 26 times

by ace_gre » Sun Jan 17, 2010 12:53 am

Hi, I would use the identities (a+b)^2 = a^2 + b^2 + 2ab and (a-b)^2 = a^2 + b^2 - 2ab
Here a = x , b = 1/x

(x + 1/x)^2 - (x - 1/x)^2 ==> 4 ab = 4 *x * 1/x = 4

Like this post

linkinpark: Master | Next Rank: 500 Posts; Posts: 124; Joined: Tue Dec 22, 2009 8:32 am; Location: Karjat; Thanked: 3 times

by linkinpark » Sun Jan 17, 2010 1:17 am

bhumika.k.shah wrote:If x is not equal to 0 ,then (x + 1/x)^2 - (x - 1/x)^2=?

A. 1/x
B. x
C. 1
D. 2
E. 4

OA E

Can i plug in #s?

in my view yes you could use numbers in this case because it involves only one variable x, if there were 2 variables then you might have to consider of scenarios like one variable is +ve and other -ve.

530->480->580
when posting a question don't post OA(even masked) before some discussion.

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review